Children can harbour more coronavirus than adults

Previous studies have suggested that children may be poor spreaders of the coronavirus, and may even be less susceptible to catching it. And in this regard the UK Chief medical officer Chris Whitty has called reopening schools “a priority”, describing how children are much less likely to come down with serious COVID-19. But a new study out of the Lurie Children’s Hospital of Chicago suggests that kids may actually play host to significant amounts of the virus. Taylor Heald-Sargent and her colleagues were looking at coronavirus genetic material - or ‘viral nucleic acid’ - inside the noses and throats of their patients, and she told Phil Sansom what they found…

Taylor - Older children had similar amounts of the pieces of virus, viral nucleic acid, to adults. And younger children actually had a bit more than the older children and the adults.

Phil - That's surprising, right? Because kids don't seem to get sick with COVID, so people - I thought - had thought that they just didn't get infected.

Taylor - So actually, and I find this quite interesting in general, is: why aren't kids getting as sick as adults? And one of the possibilities was that kids just weren't able to get infected, or if they got infected, they weren't going to be able to sustain replication. And this data argues that that's not the case. Kids are able to get infected and have replication of the virus.

Phil - Okay, how did you do this? How many kids did you look at?

Taylor - Actually, this was a clinical observation. We noticed that a few of our young kids that had recently been screened just for clinical symptoms, had very high amounts of viral nucleic acid. And when we went back and we looked at all the tests that we had done, we found this pattern. After we controlled for duration and severity of infection we were left with 145 patients. We had younger children, less than five years old; we had children aged five to seventeen years old; and then adults over 18.

Phil - So you're comparing young kids, older kids, and adults who have had the disease for the same amount of time and are physically the same amount of sick.

Taylor - Correct.

Phil - How much more virus did the younger kids have than the older kids?

Taylor - It's hard to measure directly how much more virus the children had than the adults, because what we looked at was just the nucleic acid. Children have about 10 to a hundred fold more nucleic acid compared to the older children than adults. And other previously published work by other groups have found that about that much nucleic acid correlates to having more infectious particles.

Phil - Which is quite a shock, when people thought, “oh, these kids aren't going to spread the coronaviruses, it's okay to send them back to school.” The people who were saying, “no, this isn't safe” - this is a lot of support in their corner, isn't it?

Taylor - It's an early piece of data that's needed to understand if kids have infectious virus, but we didn't look at actual infectious virus. As a scientist, I always want to be as precise as possible when I'm talking about my data. So I can't say for sure that kids have more infectious virus, but this does argue that it's possible.

Phil - The big question as well is, why aren't these kids as sick as the adults?

Taylor - I find that fascinating. What are kids doing? What's different about their bodies that allow them to be somewhat protected compared to adults? I wonder if studying children will help us figure out how to treat adults. There are several different possibilities. One of the ideas is that it has to do with the receptor for the virus, and actually where it's located in children, and how much of it there is. Another possibility is the virus just isn't able to get down into the lungs as well. And that could be related to virus, or it could be related to the immune system. Because that's a third possibility, is that the immune system in children is able to protect against viral infection. Whereas in adults, the immune system somewhat overreacts, and actually causes damage itself. I think that it's probably the immune system, but that's a hypothesis still.